Canine skin melanoma is a benign or malignant tumor occurring the cells that produce skin pigment, called melanocytes. Melanomas most often appear in the mouth, on the toes or behind the eyes as small, dark bumps or flat, wrinkled patches. If malignant, canine melanomas can spread to any part of the body, most commonly to the lymph nodes, liver, lungs and kidneys. The sooner a malignant melanoma is diagnosed, the greater likelihood your dog will survive.
Dog Breeds Prone to Melanoma
Believed to be hereditary, canine melanomas have a higher incidence in dark-skinned dogs, male dogs and dogs middle-aged or older. Certain breeds are predisposed to contracting melanomas, including Scottish terrier, Boston terrier, Airedale terrier, Cocker spaniel, boxer, Springer spaniel, Irish setter, Irish terrier, Chow-chow, Chihuahua, Doberman pinscher, poodle, dachshund, giant schnauzer, miniature schnauzer, Golden retriever and Gordon setter. Ask your vet whether your dog has a greater chance to be affected by canine melanoma.
Benign or Malignant Melanomas
Benign melanomas are called melanocytomas. They're more common than malignant melanomas, and resemble dark patches, sometimes elevated, on the skin. Your dog may have a single patch or more than one. Your vet may choose to monitor such growths carefully, or to remove them once detected. The prognosis for benign canine melanoma is very favorable.
Malignant canine melanomas may spread rapidly in your dog's mouth, under the nails, on the abdomen, on the scrotum and on the foot pads. These melanomas may look like raised, pigmented growths or infected, swollen sores. If your dog is diagnosed with malignant melanoma, the prognosis is poor.
Other Symptoms of Canine Skin Melanoma
You should become familiar with the following set of symptoms of canine melanomas. Alert your vet promptly if you notice any of these symptoms in your dog:
- Irregular skin lesions
- Tumors on the body
- Bleeding mouth or gums
- Swelling of the face
- Loss of appetite
- Marked weight loss
- Excessive drooling
- Coughing
- Difficulty swallowing
- Halitosis (bad breath)
Diagnosis of Canine Skin Melanoma
Your vet will follow these steps in diagnosing canine melanoma:
- The vet will examine skin irregularities suspected of being canine melanoma.
- The vet will order blood and urine tests, which will indicate whether melanomas may be malignant.
- During a biopsy, the vet will aspirate tissue samples from affected areas.
- Cells from tissue samples will be examined under a microscope to see whether they're cancerous.
- If your vet determines the cells are cancerous, or cannot say for certain they are cancerous, he'll send aspirate samples to an outside laboratory for confirmation of cancer.
- Further laboratory tests will determine how advanced the cancer is.
- A biopsy of the lymph nodes, x-rays and an ultrasound exam will document where the cancer has spread.
Treatment of Canine Skin Melanoma
Up to half of all canine melanomas prove to be malignant, and treatment becomes increasingly difficult as a malignant tumor spreads throughout the body. Current treatments for canine melanoma include:
- Surgical excision of the tumor and surrounding tissue, sometimes involving amputation of toes, removal of the lower or upper jaw
- Chemotherapy, if surgery is not sufficient or not possible
- Radiation therapy
- Immunotherapy
New Canine Melanoma Vaccine Shows Promise
Researchers are optimistic that a vaccine for canine melanoma, which stimulates the immune system to fight a potential tumor, will lengthen survival times of dogs afflicted with the disease. Ask your vet if the vaccine is available for your dog.